Parenting criticism

We have a four week old newborn. Lately, I get really nervous sometimes when she holds him certain ways, I don’t think she supports his head at times properly. I thought I was being over sensitive, until last week we were on FaceTime with a friend. My wife picked up the baby in the video and I could see a very subtle reaction on our friend’s face. I spoke to our friend a few days later and asked her about it and she had the same reaction. Picking up the baby under his armpits and the baby’s head flops forward or backward a little bit.

Lately, he’s been very fussy. When holding him, the slightest change in position makes him cry. He used to engage with tummy time but lately he doesn’t pick his head up, he just plants his face down and wails. Out of an abundance of caution, I wanted to take him for a physical. I tried bringing it up and she was really defensive. Insisting she knows how to hold a baby. I brought it up again a few days later and she got upset with me. Again. Now I feel I can’t say anything about it without it feeling like an attack on her ability to be a parent. I don’t want to be the “alarmist” parent, but I also need to know that my concerns are valid and for the benefit of our son and not an indictment of her ability to be a mom. Any thoughts of how to bring up concerns like this without it being met with anger or acrimony?